// A function for extracting data from an HTTP reponse
  // It takes two arguments, the XMLHttpRequest object and
  // An optional argument – the type of data that you're expecting from the server
  // Correct values include: xml, script, text, or html – the default is "", which
  // determines what the data type is based upon the content-type header
  function httpData(r, type) {
      // Get the content-type header
      var ct = r.getResponseHeader("content-type");
  
      // If no default type was provided, determine if some
      // form of XML was returned from the server
      var data = !type && ct && ct.indexOf("xml") >= 0;
  
      // Get the XML Document object if XML was returned from
      // the server, otherwise return the text contents returned by the server
      data = type == "xml" || data ? r.responseXML : r.responseText;
  
      // If the specified type is "script", execute the returned text
      // response as if it was JavaScript
      if ( type == "script" )
          eval.call( window, data );
  
      // Return the response data (either an XML Document or a text string)
      return data;
  }